Kirk Sorensen wrote:Exactly what the amount of U-233 that could be produced per unit of plutonium destroyed is not known, but the argument for going forward with the idea is pretty forgiving even if the number is bad.

That answers a couple of questions I had.

Kirk Sorensen wrote:After spending decades trying to make plutonium now we're trying to get rid of it. Consuming it in the presence of thorium is the ONLY way to do so without making more plutonium. That's another reason why uranium-plutonium MOX is such a dead end.

Mr. Sorensen,
After reading your article I'm left with the impression that Phase 2 of your three phase plan includes, if only as an option, the need to produce more plutonium in order to produce enough U-233 for Phase 3. If producing U-233 from Pu-239 is an inefficient process, and the doubling time of LFTR is on the order of a decade or two, then are we not left with the need to breed more plutonium somehow to assure a proper supply of U-233 for a transition to Phase 3? I'm left with the impression that if the conversion ratio of Pu to U-233 cannot be made better than 1.0 then we'll need a Phase 2 which includes plutonium breeders, which likely means using U/Pu MOX fuels, or a continuation of Phase 1 reactors that produce Pu from enriched U-235. There does seem to be an option of using enriched U-235 in whole or in part to start LFTRs but that seems undesirable for proliferation concerns and other reasons. Do you agree? I'm thinking that even though U/Pu MOX fuel is essentially a dead end it may be a necessary, if undesirable, step to the Phase 3 that you describe.

Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

I do hate it when my posts end up at the top of a new page since context tends to be lost as people cannot simply scroll up and read what I am referring to. In an attempt to keep context I'll highlight a couple posts from the previous page.

Jim L. wrote:The idea behind using the plutonium in a LFTR would be the two-fold objective of destroying/fissioning the Pu while producing U233 in the thermal spectrum range. This would essentially be using the LFTR as a burner, not a breeder or iso-breeder since the CR of Pu would be under 0.65 in the thermal spectrum.

So, a place like ORNL could have multiple LFTRs burning the Pu to dispose of it, generate electricity for itself or TVA, while creating the U233 that could be used in other LFTRs by power companies like Southern. I know some will be unhappy about the efficiencies of the neutron usage, but it is superior to use in U/Pu MOX fuel in a PWR or BWR. The idea of using Pu/Th fuel in a LWR is interesting, especially if the fuel elements were annular shaped and/or metal. A metallic annular-shaped fuel element would keep the centerline Tmax low, transfer heat to water better, handle FPs, gases better, reduce swelling, achieve greater/longer burn-up, and eventually would have U233 recoverable from the fuel.

I think the politics of disposing Pu may favor using a MSR, such as LFTR, since it looks far cheaper and faster than the SRS fiasco. The politicians and regulators will not care about neutron efficiency, so LFTR will look better than using chloride salts since it is further developed. Liquid metal fast reactors have their own issues and history and are less likely to be chosen. A savvy politician could sell the idea of LFTR and make thorium a buzzword - bright, shiny, and new vs. how demonize Pu and U have become. Maybe.

Jim L.

Kirk Sorensen wrote:Jim L gets the picture. The fact that plutonium burns poorly in the thermal spectrum is not really that big of a deal when you're mainly trying to get rid of it. Exactly what the amount of U-233 that could be produced per unit of plutonium destroyed is not known, but the argument for going forward with the idea is pretty forgiving even if the number is bad.

After spending decades trying to make plutonium now we're trying to get rid of it. Consuming it in the presence of thorium is the ONLY way to do so without making more plutonium. That's another reason why uranium-plutonium MOX is such a dead end.

From the article referred to we have an image of what "Phase 3" looks like:

We are currently at "Phase 1" which looks like this:

Mr. Sorensen, in this article, proposes a transitional "Phase 2" which brings us to this:

My concern is that in the process of working down the "Phase 1" column in that image fissile mass is lost, that is for every atom/kilogram/whatever of U-235 put in a current reactor a smaller number of atoms/kilograms/whatever of Pu-239 comes out. This is likely to happen again while working up the "Phase 2" column of that image, the mass of Pu-239 started with becomes a smaller mass of U-233.

In order to increase the mass of fissile material we may need a "Phase 2" which has this:

This gets back to the post which started this train of thought:

Koistinen wrote:How about using molten Pu as fuel? What are the problems in getting it to selfregulate.
I figure if you use Pu to get U-233 you don't need to be careful to get as many neutrons as possible, maybe as low as getting 1 U-233 for 10 Pu would be good enough.

Would there be a need for plutonium breeding in "Phase 2" of this plan? If so, what form would that take? Would molten plutonium reactors be a good idea?

This also gets to my other concern, what would keep us (as a nation, species, whatever) from just stopping at "Phase 2" and stay in a U/Pu cycle indefinitely? Perhaps part of the answer is here:

Kirk Sorensen wrote:I doubt the economics will support the building of many more LWRs, which is the reason that I think it may be necessary to use the LWRs we have to produce the U233 needed to start LFTRs using a thorium/plutonium MOX fuel. But if the costs of that MOX fuel are even within an order-of-magnitude of the costs of the plutonium MOX fuel anticipated to be produced at the US MOX plant in South Carolina then the whole scheme will fall apart as nonsense. Thor Energy will have to show that they can manufacture Th/Pu MOX at a reasonable price.

We can possibly produce the U-233 needed for "Phase 3" using currently existing and near future LWRs. This requires someone being able to produce the right kind of fuel rods at the right price. This means people making plans for "Phase 3" by breeding the U-233 soon, and LFTRs or some other Th/U-233 cycle reactors coming online as we retire these "Phase 1" and "Phase 2" LWRs.

I seems to me that this thread has focused on two things. First, is a discussion on what "Phase 2" should look like and what technical and political challenges may prevent it from happening. Second, articles like this would seem to be a good way to address at least some of the political problems. The more people understand the technical details the less political resistance we (as Americans, thorium energy advocates, etc.) should get.

Discuss.

Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

Sorry, plutonium burns fine in a thermal spectrum. It doesn't breed worth a s#!t. But if you breed U233 with it, the U233 can replace the Pu as the Pu burns up. All we are talking about is using Pu as the starter charge.

When it has been replaced with U233, then just enough U238 can be added to bring the overall breed rate DOWN to 1.

KitemanSA wrote:Sorry, plutonium burns fine in a thermal spectrum. It doesn't breed worth a s#!t. But if you breed U233 with it, the U233 can replace the Pu as the Pu burns up. All we are talking about is using Pu as the starter charge.

When it has been replaced with U233, then just enough U238 can be added to bring the overall breed rate DOWN to 1.

I have a feeling this has been addressed once before here:

Kirk Sorensen wrote:

KitemanSA wrote:I prefer the idea of just starting up a LFTR with a partial Pu starter charge. What I am not positive about is what percentage of the starter charge the PuF3 can be.

I think it's pretty much all or nothing. You'll either design the fuel processing system to handle a PuF3 fissile with PuF3 feed, or you'll design it to handle a UF4 fissile with UF4 feed. But not both.

Even if you are proposing using solid fuel reactors with Th/Pu fuel rods for breeding and LEU fuel rods for burning as means to create "Phase 2", as opposed to your theoretical mixed fuel 2-fluid LFTR variant, then I'm confused on why anyone would want to add U-238 to STOP the breeding once it started. Is not the point, even in "Phase 3", to continue to grow the fissile mass available? We want more fissile material, so that we can grow our nuclear power capacity. This growth is so we can replace current LWR and coal power, have the neutrons to destroy Pu and other undesirable fission products, and grow our power production capability to improve our standard of living for a growing population.

Can you explain why anyone would intentionally prevent a solid fuel reactor from converting Pu to U-233 by adding fuel rods containing U-238? This is especially confusing of the goal is to destroy the Pu, not breed more. If the goal is to breed more plutonium, for conversion to U-233 later, then we'd want the breeding ratio above 1.0, right? Shippingport APS was able to achieve a breeding/conversion ratio of about 1.01 and was considered a success. If someone can build a thermal reactor that gets a Pu to U-233 conversion ratio of even 0.5 then that would be something of a holy grail, a silver bullet, or... something else really good. The idea of first getting a thermal reactor that can attain a conversion ratio above 1.0 is hard enough, and then intentionally bringing that DOWN to 1.0 sounds like a real bad idea.

If you want to discuss the properties of a MSR that can be started from PuF with the make-up fuel being UF then, out of respect for our host, I'll ask that you start another thread to discuss that.

Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

KitemanSA wrote:Sorry, plutonium burns fine in a thermal spectrum. It doesn't breed worth a s#!t. But if you breed U233 with it, the U233 can replace the Pu as the Pu burns up. All we are talking about is using Pu as the starter charge.

When it has been replaced with U233, then just enough U238 can be added to bring the overall breed rate DOWN to 1.

Pu239 has just a 2/3 chance of fission in the thermal spectrum. Then Pu240 needs to eat another neutron so Pu241 has another shot.
Compare it with U233 with 90% chance of fission and U235 85% chance of fission.
If your reactor has zero issues with too much plutonium in it, fine, but for instance that's on of the biggest reasons PWR/BWR LEU fuel has such low burnup cycles !
It burns alright, but I have some issue with it burns "fine".

Kurt Sellner wrote: Shippingport APS was able to achieve a breeding/conversion ratio of about 1.01 and was considered a success. If someone can build a thermal reactor that gets a Pu to U-233 conversion ratio of even 0.5 then that would be something of a holy grail, a silver bullet, or... something else really good.

The Indians, with their AHWR, come to mind. The AHWR is said be an iso-breeder.

A breeder reactor/LFTR is a good aim.
With appropriate reprocessing, MSR could be a good technique.
An all-or-nothing thermal breeder LFTR might be too big a bite.
Kirk's charts on 3 stage development remind me of Indian 3 stage program. However, the route needs to be remapped for quicker progress.
There should be a first step to use thorium with RG plutonium or 20% LEU in existing reactors.http://dae.nic.in/writereaddata/.pdf_38
A blanket could be introduced to increase conversion ratio. It could follow Radkowski ideas or shipping port practice.
MSR should be independently developed. LeBlanc has the right ideas.
Thorium-U233 fuel should be introduced in the MSR.
Every step will be a useful evolution.

KitemanSA wrote:Sorry, plutonium burns fine in a thermal spectrum. It doesn't breed worth a s#!t. But if you breed U233 with it, the U233 can replace the Pu as the Pu burns up. All we are talking about is using Pu as the starter charge.

When it has been replaced with U233, then just enough U238 can be added to bring the overall breed rate DOWN to 1.

Pu239 has just a 2/3 chance of fission in the thermal spectrum. Then Pu240 needs to eat another neutron so Pu241 has another shot.
Compare it with U233 with 90% chance of fission and U235 85% chance of fission.
If your reactor has zero issues with too much plutonium in it, fine, but for instance that's on of the biggest reasons PWR/BWR LEU fuel has such low burnup cycles !
It burns alright, but I have some issue with it burns "fine".

For the start up, all you need to do is add enough to remain critical. That is the basis of MOX fuel. If you can make it work with MOX you can make it work with MF.

KitemanSA wrote:Sorry, plutonium burns fine in a thermal spectrum. It doesn't breed worth a s#!t. But if you breed U233 with it, the U233 can replace the Pu as the Pu burns up. All we are talking about is using Pu as the starter charge.

When it has been replaced with U233, then just enough U238 can be added to bring the overall breed rate DOWN to 1.

I have a feeling this has been addressed once before here:

Kirk Sorensen wrote:

KitemanSA wrote:I prefer the idea of just starting up a LFTR with a partial Pu starter charge. What I am not positive about is what percentage of the starter charge the PuF3 can be.

I think it's pretty much all or nothing. You'll either design the fuel processing system to handle a PuF3 fissile with PuF3 feed, or you'll design it to handle a UF4 fissile with UF4 feed. But not both.

I understnd Kirk's opinion, but he is working to build a breeder, I am suggesting there is a need around the world for a sustainer, something that does NOT create excess bomb making materials.

Even if you are proposing using solid fuel reactors with Th/Pu fuel rods for breeding and LEU fuel rods for burning as means to create "Phase 2", as opposed to your theoretical mixed fuel 2-fluid LFTR variant, then I'm confused on why anyone would want to add U-238 to STOP the breeding once it started. Is not the point, even in "Phase 3", to continue to grow the fissile mass available? We want more fissile material, so that we can grow our nuclear power capacity. This growth is so we can replace current LWR and coal power, have the neutrons to destroy Pu and other undesirable fission products, and grow our power production capability to improve our standard of living for a growing population.

No, the point is NOT to continue to grow the fissile mass available. It is to use SNF to start a 2.2+ Fluid LFTR and use the rest of the actinides to create a SUSTAINER for locations where you really DON'T want to breed excess bomb grade materials.

If you want to discuss the properties of a MSR that can be started from PuF with the make-up fuel being UF then, out of respect for our host, I'll ask that you start another thread to discuss that.

KitemanSA wrote:I understnd Kirk's opinion, but he is working to build a breeder, I am suggesting there is a need around the world for a sustainer, something that does NOT create excess bomb making materials.

A reactor that produces more fissile material than what it consumes does not necessarily produce more bomb making materials. As someone that has retired from the Navy as an engineer I assume that you would understand the difference between reactor grade and weapon grade materials.

KitemanSA wrote:No, the point is NOT to continue to grow the fissile mass available. It is to use SNF to start a 2.2+ Fluid LFTR and use the rest of the actinides to create a SUSTAINER for locations where you really DON'T want to breed excess bomb grade materials.

As I understand your proposed "2.2+ fluid LFTR" it would be highly efficient at producing weapon grade plutonium. I have pointed out why I believe this in the other threads that you have proposed your reactor design. I am willing to discuss this with you in detail but you have to show you are willing to do so by starting another thread on this in an appropriate place. This is not the place to debate the merits of your proposal.

We do in fact need more fissile material since if we are going to replace the coal and natural gas power plants we have today with nuclear power then we need fuel for them. We can produce that fuel in several ways, mining and enriching U-235 is one of them but that is not very attractive for many reasons, primary among them is the concerns of the enrichment facilities being commandeered to produce weapons. There is also the matter of increasing the mass of fissile material to account for the growing demand for energy. Right now many people live in poverty because of the lack of inexpensive energy, if we expect to live the global population to the standard of living you and I enjoy, and not burn stuff to do it, then we are going to need a lot of nuclear fuel and be able to produce it quickly.

Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

Except if you removed the Pu, the reactor would stop for lack of fuel.

It would not be Pu that would be extracted, it would be the Np, which would be placed in a decay tank for Pu extraction. Of the most likely NP isotopes extracted from the fuel there would be Np-237, a long lived isotope valuable for Pu-238 production, and Np-239, a short lived isotope that decays quickly to Pu-239. It is trivial to separate the Pu-239 from the Np. Once separated then it would have to be returned to the reactor or it would run out of fuel, as you claim, unless it was fed with more LEU, SNF, or even thorium or DU. That extracted Pu-239 would be of a very high purity, weapon grade purity.

KitemanSA wrote:It you are concerned about making weapons grade material, then a standard 2 Fuel LFTR is the best bomb factory around. Getting clean U233 should be quite easy.

Getting clean U-233 is not easy since a significant portion of that would be U-232. Like above what is extracted from the fuel is not the uranium itself but its parent isotope. This Pa will come in two dominant isotopes Pa-232 and Pa-233, once they decay (which they both do in a matter of days) the U-233 and U-232 will be difficult to separate. U-233 is only a weapon grade material in theory, when contaminated with other isotopes it is worthless for weapons.

I don't know the rate at which such a reactor could refine SNF to Pu-239 but I am quite certain that it would be of a purity that is well above weapon grade.

The extraction of the Pu at this point may actually improve the performance of such a reactor since Pu-239 is a poor fuel in the thermal spectrum. To account for the loss of fuel mass one could put in Th instead.

There is no doubt in my mind that your proposed reactor is capable of consuming SNF, LEU, and WGPu but there is a place in the system in which WGPu can be extracted and diverted. There would have to be some sort of other system to prevent the WGPu from existing in the system as a separated byproduct. This can be done by not extracting the Np, which means the reactor cannot be used to produce RTG fuel, neutron losses from not separating the Np poisons from the reaction, a greater need for more fuel, and production of TRUs.

Alternatively the feedstock fuel should be free from any uranium isotopes, and consist only of Th and Pu. There will still be TRUs produced but if there was no Np extraction the TRU waste left over should be suitable as starter fuel for another LFTR since it is effectively RGPu. If there is Np extraction the TRU waste would be minimal and the purity of the Np-237 would be much higher.

As with my other thought experiments I hand waved over some details but I do believe my calculations are generally correct. I'd appreciate any corrections. I'd also like to see this moved to another thread since I feel we've gone off topic here.

Kiteman, please start a new thread on your proposal in an appropriate sub-forum on your design and we can discuss the details further.

Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.

KitemanSA wrote:It you are concerned about making weapons grade material, then a standard 2 Fuel LFTR is the best bomb factory around. Getting clean U233 should be quite easy.

Getting clean U-233 is not easy since a significant portion of that would be U-232.

In fact, getting clean U233 would be easier than getting clean Pu239, IMHO. All it needs is two additional fluoride volitility reactors and a modified hold-up tank.

Kiteman,
Now I KNOW we're going off topic here. If you want to continue this discussion then start a new thread. This sounds like something better discussed in the proliferation sub-forum or the liquid fluoride reactor design sub-forum. Send me a PM once you've started the thread and I'll join you there.

Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.